Blood coagulation activity is an important item for obtaining an index used for screening the deficiency of an extrinsic coagulation factor or monitoring the abnormality of the liver function and an anticoagulant treatment with oral administration.
Such a blood coagulation test mainly uses a PT (Prothrombin time) measurement method, an APTT (Activated Partial Thromboplastin Time) measurement method, a fibrinogen test, and the like. These measurements and tests are executed by using large-sized analysis apparatuses in hospitals. When conducting a test by using the PT measurement method and the APTT measurement of these methods, a protein (thrombomodulin or ellagic acid) and calcium ions which coagulate blood are mainly mixed as coagulation reaction triggers in blood plasma, the time (coagulation point) from the start of mixture to the completion of coagulation is measured, and a delay time is estimated by comparing the measured time with a standard blood plasma result.
This PT method of measuring the blood coagulation activity of an endogenous/extrinsic blood coagulation route has currently been internationally standardized (PT-INR) and considered as a test item which is high in repeatability and reliability. For example, first of all, an agitation resistance scheme is available as a method of physically executing the PT method. The agitation resistance scheme is a method in which a sample (specimen) is introduced together with an activating agent, and a blood coagulation time is measured from a rise in agitation resistance when the sample and the agent are agitated with a fin.
In addition, as a method of executing the PT measurement method, there is available a light scattering method (see patent literatures 1, 2, and 3). The light scattering method is a method in which a blood plasma as a target is mixed with a reagent containing a component for promoting coagulation activation in a measurement vessel, light is caused to enter the vessel, and a blood coagulation time is measured by measuring a change in the amount of scattered light of the incident light. Methods of obtaining a blood coagulation time from the amount of scattered light include a method directly using the amount of scattered light, a method using the derivative value of the amount of scatted light, and a method of obtaining the time until the amount of scattered light reaches a predetermined value (see patent literature 1).
The above agitation resistance scheme and light scattering method are currently generally used for the test of blood coagulation in many cases. In addition to them, a heat conduction scheme, a crystal oscillator scheme, an aggregation measurement method using magnetic beads (see patent literature 4), and the like have been developed.
In addition, the present inventors have proposed a method of testing coagulation activity by measuring a flow velocity using an SPR (Surface Plasmon Resonance) measurement method using a chip having a micro flow channel. In this test, first of all, a blood plasma sample completely activated by being mixed with coagulation activating agents (ellagic acid and calcium chloride) is prepared immediately before measurement. Subsequently, the blood plasma sample is introduced into the flow channel filled in advance with a buffer solution to convert the flow velocity of blood plasma flowing in the flow channel into a coagulation time (see patent literature 5). Flow velocity measurement using such a micro flow channel has a merit that it can quickly measure coagulation activity by using a small amount of specimen.